Heartworm is a parasitic virus, and there only one manufacturer with a drug to treat advanced stages.
Heartworm is spread from infected mosquitoes to dogs and can be fatal, and it attacks more than just the heart.
"Each time the heart pumps, that worm is moving around and it can cause damage to the lungs and the valves of the heart," said Dr. Shari Lyons, Zionsville Country Veterinary Clinic.
Heartworm can be difficult to treat, because symptoms do not show up until the later stages of the disease. Now, it has become even tougher to fight.
The company Merial, the only maker of the FDA approved medicine to treat adult heartworm, sent notices to vets that it officially ran out of the medication this month.
"Some sort of a manufacturing glitch that they're working out,” said Dr. Lyons. “Because of that, it's open-ended. We don't know if and when it'll come back.”
Immiticide is used to treat the more advanced stages of heartworm. Until more is available, Dr. Lyons says detection is important. Immature heartworm, microfilaria, can be treated. For the advanced stage, the one that does the most damage, antibiotics can manage the effects.
With a shortage, prevention becomes that much more important. Dog owners should know that while there is a lack of medicine to treat heartworm, there are still plenty of heartworm prevention products still available.
However, products like HeartGuard and Interceptor should not be given until your dog is tested. If prevention medicine is given when he or she is already infected with adult heartworm, it could make things worse.
"That will keep them from getting any further heartworm, so you can be on that during the time you're waiting to get rid of all the adult worms,” said Dr. Lyons.
Dr. Lyons' clinic has seen three cases of heartworm in the last month. All three had been on heartworm prevention, but it was medicine they got from online pharmacies.
Dogs who have heartworm are not supposed to exercise, because that can spread the parasite even faster.